Re: [CAD_CAM_EDM_DRO] BobCad??

> My next goal is to be able to get BobCad to do a complex 3D surface. I
> expected this to be straightforward when I bought the software, but now I
> think otherwise. I want to import a 3D model and generate g-code, not
> redraw my 3D model in BobCad.

James,

As far as importing models into BobCAD v17, most will need to be
modified by you. On anything beyond wireframe is often a long, tedious, or
non-feasible task. Wireframes almost invariably need to be tweaked for
'skin'-ing. (intersections, inside curves, entity count between 'rungs'...)
Solids and surfaces have to be imported (IGES) as edges in BobCAD. Each
surface 'patch' having a line perimeter means two entities of almost the
exact same position and size wherever surface patches meet. A real pain to
clean up. Then you've still the tweaking process.
For business use, I'd recommend moving up to a CAD/CAM program that
handles surfaces and solids, and can import current IGES files.

- Keith Rumley

Now, if you've more time than money, which includes most :)...
To make 3D complex items, I found that it worked best to manually create
a new wireframe offset from the original model by the cutter center
distance*. Next, use the skin tool with an 'end radius' of zero and a
constant stepover to create the toolpath, the stepover amount determining
surface smoothness. ('distance between lines' = stepover)
Not only does this simplify dealing with double entities and
less-than-perfect models, but you can modify the wireframe in another CAD
program, say a legacy version of ACAD, or IntelliCad, which has better view
and entity manipulation.
Certain details, such as steep walls and multiple sharp corners, usually
need a separate toolpath.
If you use the original model, BobCAD's offsetting tend to result in
gouges, wierd tangents, and the like. With a zero tool diameter, BobCAD
won't do the goofy offsetting tricks, and your toolpath will fit your
boundaries exactly.

* A good way to get a start on the new offset wireframe is to use the skin
tool with a large distance between lines, then from the newly created
offsets you can 'chain' select the edge lines you need. 'Copy' them to
clipboard, 'Undo' back past the skin command, 'paste' from clipboard.
Wa-La! Do it once in each of the two perpendicular directions of the
surface 'patch'.
In the skin tool under the 'Connect' heading select 'None', otherwise
it's near impossible to select the contour edges you want without getting
extra entities along with.
To get just the two offset edges, use a 'distance between lines' greater
than the distance between your surface boundaries. Use less distance if you
need cross-sectional segments.



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